1. Field of the Invention
This invention is related to the field of digital systems and, more particularly, to connecting the systems to network displays.
2. Description of the Related Art
Digital systems of various types often include, or are connected to, a display for the user to interact with the device. The display can be incorporated into the device. Examples of incorporated displays include the touchscreen on various smart phones, tablet computers, or other personal digital assistants and laptops with the screen in the lid. The display can also be connected to the device via a cable. Examples of the connected display include various desktop computers and workstations having a separate display that resides on the desk in front of the user. Some desktops also have an incorporated display (e.g. various iMac® computers from Apple Inc.). The display provides a visual interface that the user can view to interact with the system and applications executing on the system. In some cases (e.g. touchscreens), the display also provides a user interface to input to the system. Other user input devices (e.g. keyboards, mice or other pointing devices, etc.) can also be used.
In the above cases, the digital system includes hardware to interface directly to the display, driving the control signals to control the display of each pixel (e.g. red, green, and blue control signals) in real time as the pixels are displayed on the screen. The hardware generates the timing for the display as well, such as the vertical and horizontal blanking Interfaces such as video graphics adapter (VGA), high definition media interface (HDMI) etc. can be used to connect to these displays.
More recently, network displays are becoming popular. In a network display, the connection between the digital system and the display is a network such as Ethernet, WiFi networks, etc. The digital system provides a frame of pixels to be displayed as the data payload in one or more packets transmitted over the network, and the network display receives the packets and controls its own internal timing to display the received frames. Accordingly, the network display is no longer truly a real time device. However, latency between the system and the network display is still an important factor, since the user is viewing the display and may be interacting with the system as well. The network display interface includes the network protocol stack and the operating system, between the application that generates the frames and the network display. The operating system and the network protocol stack are not typically real time, and so the delays can be unpredictable. Additionally, in some cases, the network display is used to display the same frames as the local display (incorporated or directly connected) in “mirror mode” (e.g. when making a presentation). Again, the latency to provide the frames to the network display affects the user's perception of whether or not the system is working properly.